Write jog value determination for a disk drive
View Patent ↗A disk drive for determining a write jog value is disclosed. The disk drive comprises: a disk; a head including a reader and a writer; and a processor. The processor controls operations in the disk drive including: commanding the reader to track follow on a first track, wherein the writer is located over an uncalibrated track position; commanding the writer to write a first test pattern on a section of the disk; commanding the writer to move by a plurality of step amounts to write a plurality of test patterns; commanding the reader to move by a second plurality of step amounts to read the plurality of test patterns; determining a reader signal value associated with each test pattern; determining the uncalibrated track position based on the read signal values; and determining the write jog value based on the distance between the first track and the uncalibrated track position.
1. A method for determining a write jog value for a head in a disk drive, the head including a reader and a writer for reading and writing on the surface of a disk, the method comprising:
using the reader to track follow on a first track, wherein the writer is located over an uncalibrated track position;
using the writer to write a first test pattern on a section of the disk;
moving the writer by a plurality of step amounts to write a plurality of test patterns;
moving the reader by a second plurality of step amounts to read the plurality of test patterns;
determining a reader signal value associated with each test pattern;
determining the uncalibrated track position based on the read signal values; and
determining a write jog value based on the distance between the first track and the uncalibrated track position.
2. The method of claim 1 , wherein the read signal value comprises a read signal amplitude value and determining the uncalibrated track position further comprises:
determining a reader position associated with a highest read signal amplitude for each of the plurality of test patterns; and
calculating the uncalibrated track position by averaging the reader positions.
3. The method of claim 1 , wherein the disk comprises an embedded servo pattern including a plurality of servo wedges separated by data wedges.
4. The method of claim 1 , wherein the plurality of step amounts are approximately equal.
5. The method of claim 1 , wherein the plurality of step amounts are of differing sizes.
6. The method of claim 1 , wherein the disk includes a plurality of track lands having track centers and a plurality of grooves separating the track lands.
7. The method of claim 1 , wherein the plurality of test patterns comprise a periodic pattern.
8. The method of claim 1 , wherein using the writer to write the first test pattern on a section of the disk and moving the writer by a plurality of step amounts to write a plurality of test patterns further comprises:
starting the writer at a beginning position to write a first test pattern across a first section of the disk, the beginning position being determined by a predetermined offset from the uncalibrated track position; and
stepping the writer across the uncalibrated track position to an ending position to write a last test pattern across a last section of the disk, the ending position being determined by a second predetermined offset from the uncalibrated track position, such that a plurality of test patterns are written between the beginning position and the ending position.
9. The method of claim 8 , wherein the difference between the beginning position and the ending position is approximately one track.
10. The method of claim 9 , wherein the reader begins to read the plurality of test patterns approximately three tracks away from the uncalibrated track position.
11. The method of claim 1 , further comprising determining a write jog value for a pre-defined number of different tracks across the disk during manufacture of the disk drive.
12. The method of claim 11 , wherein the write jog values for the pre-defined number of different tracks across the disk are used to calculate coefficients for a write jog value interpolation equation for write jog value calculation, the coefficients for the write jog value interpolation equation being stored in at least one of a reserve cylinder of the disk or a non-volatile memory of the disk drive.
13. The method of claim 1 , wherein moving the writer by a plurality of step amounts to write a plurality of test patterns occurs over one revolution of the disk.
14. The method of claim 1 , wherein the step amounts comprise a predetermined percentage of a track width.
15. A disk drive comprising:
a disk;
a head including a reader and a writer for reading and writing on a surface of the disk;
a processor for controlling operations in the disk drive to determine a write jog value for the head, the operations comprising:
commanding the reader to track follow on a first track, wherein the writer is located over an uncalibrated track position;
commanding the writer to write a first test pattern on a section of the disk;
commanding the writer to move by a plurality of step amounts to write a plurality of test patterns;
commanding the reader to move by a second plurality of step amounts to read the plurality of test patterns;
determining a reader signal value associated with each test pattern;
determining the uncalibrated track position based on the read signal values; and
determining a write jog value based on the distance between the first track and the uncalibrated track position.
16. The disk drive of claim 15 , wherein the read signal value comprises a read signal amplitude value and determining the uncalibrated track position further includes operations comprising:
determining a reader position associated with a highest read signal amplitude for each of the plurality of test patterns; and
calculating the uncalibrated track position by averaging the reader positions.
17. The disk drive of claim 15 , wherein the disk comprises an embedded servo pattern including a plurality of servo wedges separated by data wedges.
18. The disk drive of claim 15 , wherein the plurality of step amounts are approximately equal.
19. The disk drive of claim 15 , wherein the plurality of step amounts are of differing sizes.
20. The disk drive of claim 15 , wherein the disk includes a plurality of track lands having track centers and a plurality of grooves separating the track lands.
21. The disk drive of claim 15 , wherein the plurality of test patterns comprise a periodic pattern.
22. The disk drive of claim 15 , wherein using the writer to write the first test pattern on a section of the disk and moving the writer by a plurality of step amounts to write a plurality of test patterns further includes operations comprising:
starting the writer at a beginning position to write a first test pattern across a first section of the disk, the beginning position being determined by a predetermined offset from the uncalibrated track position; and
stepping the writer across the uncalibrated track position to an ending position to write a last test pattern across a last section of the disk, the ending position being determined by a second predetermined offset from the uncalibrated track position, such that a plurality of test patterns are written between the beginning position and the ending position.
23. The disk drive of claim 22 , wherein the difference between the beginning position and the ending position is approximately one track.
24. The disk drive of claim 23 , wherein the reader begins to read the plurality of test patterns approximately three tracks away from the uncalibrated track position.
25. The disk drive of claim 15 , wherein the processor further performs operations comprising determining a write jog value for a pre-defined number of different tracks across the disk during manufacture of the disk drive.
26. The disk drive of claim 25 , wherein the write jog values for the pre-defined number of different tracks across the disk are used by the processor to perform further operations comprising calculating coefficients for a write jog value interpolation equation for write jog value calculation, the coefficients for the write jog value interpolation equation being stored in at least one of a reserve cylinder of the disk or a non-volatile memory of the disk drive.
27. The disk drive of claim 15 , wherein moving the writer by a plurality of step amounts to write a plurality of test patterns occurs over one revolution of the disk.
28. The disk drive of claim 15 , wherein the step amounts comprise a predetermined percentage of a track width.